Update README.md

fix MRL link format

README.md

@@ -5455,7 +5455,7 @@ Prompt of s2s task(e.g. semantic textual similarity task):
 Instruct: Retrieve semantically similar text.\nQuery: {query}
 ```
 
-The models are finally trained by [MRL]((https://arxiv.org/abs/2205.13147)), so they have multiple dimensions: 512, 768,
+The models are finally trained by [MRL](https://arxiv.org/abs/2205.13147), so they have multiple dimensions: 512, 768,
 1024, 2048, 4096, 6144 and 8192.
 
 The higher the dimension, the better the performance.